FIG. 1(a) shows current-voltage characteristics of a solar cell module, in which an electric current in a voltage of 0V is referred to as a short-circuit current Isc and a voltage in a current of 0 A is referred to as an open-circuit voltage Voc. Additionally, FIG. 1(b) shows power-voltage characteristics. When a point where the power becomes maximum is defined as an operating point, an operating voltage with respect to the operating point is referred to as a maximum operating voltage Vop and an operating current is referred to as a maximum operating current Iop.
Characteristics of the solar cell module can be represented by an expression (1) using parameters which are, I: output current [A], Is: reverse saturation current [A], V: output voltage [V], Isc: short-circuit current [A], T: solar cell device absolute temperature [K], k: Boltzmann constant [J/K], Rs: series resistance of wiring and so on connecting solar cells to each other [Ω], q: electric charge amount of electrons [C], Rsh: parallel resistance [Ω], n: diode junction constant, p: solar radiation intensity [kW/m2] and Ncell: the number of solar cells included in the solar cell module.I=Isc·p−Is·{exp(q(V/Ncell+Rs·I)/(n·k·T))}−(V/Ncell+Rs·I)/Rsh  (1)
Ib: output current [A] and Vb: output voltage [V] in a solar radiation intensity Eb and a temperature Tb can be calculated by an expression (2) and an expression (3) by using Ia: output current [A], Va: output voltage [V], Isca: short-circuit current [A], Rsa: series resistance [Ω], a temperature coefficient of the short-circuit current α [A/C.°], a temperature coefficient of the open-circuit voltage β [V/C.°] and a curve correction factor K in a solar radiation intensity Ea (1 kW/m2) and a room temperature Ta (298K).Ib=Ia+Isca·(Eb/Ea−1)+α·(Tb−Ta)  (2)Vb=Va+β·(Tb−Ta)−Rsa·(Ib−Ia)−K·Ib·(Tb−Ta)  (3)
PTL 1 can be cited as a related art for grasping characteristics of each solar cell module.
In PTL 1, basic characteristic values of three points of temperatures as references are calculated and curvilinear interpolation is performed to these values to obtain basic characteristic values at a designated temperature.
PTL 2 can be also cited as another related art. In PTL 2, in the case of calculating a power generation amount at each temperature when solar radiation energy is 1 kW/m2, first, current-voltage characteristics are calculated by defining solar radiation energy as 1 kW/m2 and a solar cell temperature as 25° C. Next, a generation current and a voltage in the current-voltage characteristics at 25° C. are corrected in accordance with the temperature by using expressions (2) and (3) as correction expressions for correcting the generation current and the voltage depending on the temperature in an power generation amount correction unit.